Housing has evolved throughout the ages, with modifications arriving in concurrence with culture, artistry and necessity. The current state of housing in this country is an affordable dwelling unit built with indigenous materials. Far from the stone structures of aristocracy, the majority of homes, even the expensive ones, utilize generally a wood veneer frame supported on a concrete foundation and/or steel or wood girder beams. More expensive homes may feature a brick exterior, but this is usually a decorative veneer. Most have a wood, vinyl or aluminum cladding over the wood “rough” or main structural framing. The wooden rough framing is fastened together with either nails or screws.
Homes are also built with metal framing, with a 12 to 24 gage metal, bent to mimic the cross-section of a milled wood unit, stud framing.
When this stud framing is used, the construction consists usually of either a 2×4 or 2×6 wooden stud with a cross sectional dimension of 1½″×3½″ or 1½″×5½″, respectively, at a distance of 16″ or 24″ on center. This is built over a plate, which sits on a floor deck generally consisting of 2×8, 2×10 or 2×12 dimensional milled lumber. New technology may feature different elements, such as floor trusses or composite beams and joists of various configurations, but the building components generally act in similar structural fashion.
The method of concrete footing over undisturbed soil, excavated to a point at which frost cannot cause upheaval of the ground, with a concrete foundation above it, a sill plate bolted into the concrete, a floor deck over the sill, walls over the floor deck, another floor deck or roof above, and roof rafters to complete the roof, is known as Platform Framing. The standard method for the construction of homes in this country.
When solid masonry is used in lieu of wood framing, the overall method is roughly similar. The wall, for example, in a two story structure, goes from the concrete foundation wall to the roof, and floor joists are framed within the wall, usually “fire cut,” or with an angle which, in a fire, can allow the floor to drop down without toppling the wall.
In a mobile home, the construction is usually somewhat identical to a wood frame home, with consideration given to the dynamic loads due to transportation. Modular homes, by their nature, are usually fabricated in a factory, but the notion that the dwelling unit is “modular” does not necessarily mean that there is an inherent additional strength in the structure.
The problem with all of these methods of construction lies in their inherent compartmentalization of components and their inability to interact with each other. When a force is applied to one element of the building, the only awareness of this force sensed by other components may be in the movement of these components once the structure starts to fail. This failure can be as a result of one component pushing against another as a result of a wind load, but the other piece cannot “feel” the force on its preceding component and thus provide any assistance to it. Also, components are fastened in a way as to resist gravity loads, but allow little or no protection against the torsional, lateral or other severe forces as a result of a cataclysmic wind event.
Also, the custom nature of domestic housing creates a cost factor that would be eliminated in a modular house, with the structural strength built into the design, and not required to have structural rigidity added at extra cost. In addition, the modular design results in more controlled costs due to the standardization of framing elements.